Make arguments like Context.GrobName accessible as symbol lists

Documentation/snippets/using-postscript-to-generate-special-note-head-shapes.ly

 %% DO NOT EDIT this file manually; it is automatically
 %% generated from LSR http://lsr.dsi.unimi.it
 %% Make any changes in LSR itself, or in Documentation/snippets/new/ ,
 %% and then run scripts/auxiliar/makelsr.py
 %%
 %% This file is in the public domain.
-\version "2.16.0"
+\version "2.17.6"
 
 \header {
   lsrtags = "editorial-annotations, really-cool, scheme-language, tweaks-and-overrides"
 
   texidoc = "
 When a note head with a special shape cannot easily be generated with
 graphic markup, PostScript code can be used to generate the shape.
 This example shows how a parallelogram-shaped note head is generated.
 
 "
   doctitle = "Using PostScript to generate special note head shapes"
 } % begin verbatim
 
 
 parallelogram =
   #(ly:make-stencil (list 'embedded-ps
     "gsave
       currentpoint translate
       newpath
       0 0.25 moveto
       1.3125 0.75 lineto
       1.3125 -0.25 lineto
       0 -0.75 lineto
       closepath
       fill
       grestore" )
     (cons 0 1.3125)
     (cons -.75 .75))
 
-myNoteHeads = \override NoteHead #'stencil = \parallelogram
-normalNoteHeads = \revert NoteHead #'stencil
+myNoteHeads = \override NoteHead.stencil = \parallelogram
+normalNoteHeads = \revert NoteHead.stencil
 
 \relative c'' {
   \myNoteHeads
   g4 d'
   \normalNoteHeads
-  <f, \tweak #'stencil \parallelogram b e>4 d
+  <f, \tweak stencil \parallelogram b e>4 d
 }